Generally a diesel engine is used as the engine in a wheel loader. The diesel engine produces nitrogen oxide since the inside of the combustion chamber has an excessive amount of nitrogen, and thus the exhaust gas includes nitrogen oxides. A hydraulic excavator, for example, described in Japanese Patent Laid-open No. 2012-237232 includes a selective catalyst reduction device, an injection device, a reducing agent tank, a reducing agent pump, and a reducing agent pipe in order to remove the nitrogen oxides in the exhaust gas. The reducing agent pump feeds a reducing agent such as a urea aqueous solution stored in the reducing agent tank to the injection device through the reducing agent pipe, and the injection device injects the reducing agent into the exhaust gas upstream from the selective catalyst reduction device. As a result, the nitrogen oxides in the exhaust gas exhausted from the engine are reduced to nitrogen.